1. Field of the Invention
The present invention relates to a lithographic apparatus and an associated device manufacturing method.
2. Description of the Related Art
Lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, a patterning device may be used to generate a desired circuit pattern corresponding to an individual layer of the IC, and this pattern can be imaged onto a target portion (e.g. comprising one or more dies) on a substrate (silicon wafer) that has been coated with a layer of radiation-sensitive material (resist).
In general, a single substrate will contain a network of adjacent target portions that are successively exposed. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion in one go, and so-called scanners, in which each target portion is irradiated by scanning the pattern through the projection beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction.
The processing of substrates requires that the substrates, destined for processing, are supplied to the lithographic apparatus and, after processing, the processed substrates are removed from the apparatus. Generally, a track brings the substrates, which are to be processed to a loading station. From this loading station, the substrates are moved one-by-one to the processing unit of a lithographic apparatus, in which the actual processing of the substrate takes place.
Processed substrates are then generally moved, one-by-one, from the processing unit of the lithographic apparatus to a discharge station. A track generally takes the processed substrates away from the discharge station.
Other ways of supplying the substrates to the lithographic apparatus and removing substrates from the lithographic apparatus are known to the person skilled in the art, such as, for example, the use of a front opening unified pod. The front opening unified pod contains a plurality of substrates, and supplies them one-by-one to the loading station.
In known lithographic apparatus, a transfer unit for transferring a substrate, which is to be processed, from a loading station to the processing unit and for transferring the processed substrate from the processing unit to a discharge station is provided. The known transfer unit comprises a loading robot and a discharge robot. The loading robot takes a substrate, which is to be processed, from the loading station to the processing unit of the lithographic apparatus. The discharge robot then takes the processed substrate from the processing unit of the lithographic apparatus to the discharge station.
This known transfer unit setup is quite expensive, and requires a relatively large amount of space.